As the high speed packet access (HSPA) and Internet protocol (IP) multimedia subsystem (IMS) are introduced into a 3rd Generation Partnership Project (3GPP) network, it is expected that the user plane data traffic will significantly increase in the coming several years. In order to improve data transmission performance of the 3GPP system and reduce the costs of network investment by the operator, the 3GPP organization has researched a network architecture called One Tunnel, which is referred to as “One Tunnel” or “Direct Tunnel” network architecture in the specification (briefly called One Tunnel). Particularly, a user plane tunnel is directly established between a radio network control (RNC) and a gateway general packet radio service (GPRS) support node (GGSN) to replace the existing two tunnels respectively between the RNC and a serving GPRS support node (SGSN) and between the SGSN and the GGSN to strip the user plane function from the SGSN node, so as to save the operator's investment on the capacity expansion of the SGSN user plane in order to cater to the traffic growth of a network user plane caused by the HSPA. In brief, the One Tunnel architecture may be generalized as a flattening of user plane levels, in which the core network retains one layer of user plane node and one tunnel is established between the access network and a user plane entity of the core network.
In the 3GPP system, the data transmission between the access network and the core network user plane uses a GPRS tunnel protocol (GTP) technology. When one end of a GTP tunnel receives a packet data sent from a peer end, the peer end locates a user plane context according to tunnel end identity (TEID) information carried in a GTP header in an external layer of the packet data and then forwards the data according to routing information stored in the context. If a node at one end of the GTP tunnel may release the user plane context due to node reset or other abnormal circumstances, once receiving the data sent from the peer end of the GTP tunnel, the node cannot locate the corresponding user plane context or forward the received packet data normally, and therefore, merely discards the received data. According to the requirements of the GTP protocol, if the GTP data packet is received but the user plane context cannot be located, an error indication message needs to be sent to the peer end while the data packet is discarded, so as to notify the peer end that the tunnel is invalid and not to send data via the current tunnel any more.
In the One Tunnel architecture, the user plane has only one data tunnel established between the RNC and the GGSN. Once the RNC releases air interface resources and context of the user due to abnormal circumstances such as reset, a relevant downlink data tunnel between the relevant RNC and the GGSN becomes invalid. If the GGSN delivers a data to the RNC via the invalid downlink data tunnel, the GGSN inevitably receives an error indication message, i.e., an error indication, returned from the RNC. According to the current processing mechanism, in this case, the GGSN deactivates a packet data protocol (PDP) context to release the entire IP bearer. If a user wants to recover the data transmission later, the user must reactivate the PDP to establish the IP bearer.
In the above system, after the invalidation of the downlink data tunnel between the RNC and the GGSN, the user has to reactivate the PDP to establish the IP bearer once again to recover the data transmission. Such reactivation operation inevitably affects the speed of the data transmission recovery and causes the affected users to appear offline, which is undesirable in the 3GPP systems. In addition, reactivation of the PDP cannot ensure the IP address of the IP bearer unchanged, and the application based on the 3GPP network is therefore easily interrupted due to the change of the IP address.